1. Field of the Invention
Embodiments according to the invention relates to blade servers. More particularly, embodiments according to the invention relate to connecting multiple blades to a single host bus adapter in a blade chassis.
2. Description of the Related Art
Effectively deploying multiple devices in a network environment becomes an increasingly complex task as transmission data rates, processor speeds, and storage capacities increase. Storage area networks (SANs) have been developed as specialized high-speed networks, referred to as fabrics, to connect computer systems, control software, and storage devices over the fabric. SANs typically allow block level input/output (I/O) rather than file-level access. Thus, every device connected to a SAN fabric appears as a locally attached device to other devices on the fabric.
Although a SAN allows for relatively simple interchangeability of components without disrupting other components, physical space available for components also presents a challenge. Blade servers have been developed in part to overcome traditional server-rack design restrictions. Blade server architecture allows multiple processor modules to be housed in a single chassis. Typically, the chassis provides the power supply for any attached blade servers, while each blade server has its own processor, memory, and possibly disk storage. Blade servers are designed for high-density computing applications, including SANs.
FIG. 1 shows components in a prior art blade chassis 101. The blade chassis 101 includes a Fibre Channel switch 102 and a series of host blades 104. Each host blade 104 has a processor 106, a bridge 108, memory 109, and a host bus adapter (HBA) 110. Conventionally, the HBA 110 is a daughter board connected to the host blade 104. Each memory 109, connected to the bridge 108, contains queues that comprise command and completion rings for data sent to and received from the HBA 110. The bridge 108 handles I/O processes and provides an interface between devices internal to and external to the host blade 104 (e.g., central processing unit (CPU) 106, HBA 110). As an example, the bridge 108 can provide PCI-X or PCI-Express connections to the HBA 110. Each HBA 110 connects the respective host blade 104 to other network and storage devices 114 on an enterprise fabric 112 via the Fibre Channel switch 102. As is known in the art, each HBA 110 has a unique World Wide Name (WWN), which identifies the HBA 110, and thus the respective host blade 104, to the Fibre Channel switch 102 and other devices on the enterprise fabric 112.
As seen in FIG. 1, modern server environments typically connect an HBA with each host blade. However, the actual data throughput on each of these HBAs is typically quite small compared to the capacity and link speeds that are possible in modern networks. In other words, a modern server typically cannot saturate its on-board HBA. Despite the advances in SAN and server technology, network designers are continuously seeking new ways to increase storage space, processing capabilities, and data transmission rates, while decreasing the overall physical network size.